Author

Ahmed Essam

Date of Award

December 2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

First Advisor

Wayne Seames

Abstract

The rising global demand for addressing global warming necessitates the development of renewable-based alternatives to current fossil fuel-based chemicals and fuels. Lignocellulosic biomass is the most abundant energy source following fossil fuels. As a result, agricultural residues such as corn stover have attracted substantial interest for utilization as a potential feedstock for renewable chemicals.Previous research work at the University of North Dakota showed promising results in converting corn stover sugars into chemical building blocks. The most crucial of these chemicals is lactic acid, which can be used in multiple applications including food, pharmaceuticals, and biodegradable plastics. Traditionally, lactic acid is produced through fermentation. The high costs and time-consuming nature of the fermentation process acts as a barrier for lactic acid to compete with fossil-based alternatives. Substitute catalysis-based technologies are proposed as more cost effective and scalable. These advantages should allow lactic acid and other renewable chemicals to be more abundantly available at a reasonable price and be converted into more valuable products such as biodegradable plastics. Upon the success of this research, the market value of corn stover is expected to increase. This will create an additional revenue stream for farmers, thereby incentivizing them to collect stover from fields, secure the feedstock supply chain, and reduce the carbon footprint of chemical production. The goal of this research was to translate a batch, lab-scale catalytic reaction that used a powdered Sn-beta zeolite to a continuous bench-scale fixed bed reactor system utilizing catalysts in the pellet form. This catalytic reaction converts sugars derived from the cellulosic (via glucose) and hemicellulosic (via xylose) portion of corn stover into a product mixture of high-value chemicals used for polymer production. Two catalysts, tin-doped beta zeolite, and tin-doped commercial silica, were compared for their yield performance. The reaction conditions were optimized aiming for a product mixture that has a high concentration of lactic acid plus smaller concentrations of acetic, formic, and levulinic acids. Unfavorable results of yields that did not exceed 28 wt.% of inlet carbon when running in a continuous fashion suggest that neither of the Sn-beta zeolite pellets nor the Sn-silica pellets, as formulated in this work, can be used to scale up the initial technology under the conditions examined. While more operationally challenging, exploring the use of powdered Sn-doped beta zeolite catalyst in a continuous fashion is recommended based on the conclusions of this study.

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